11. Stockholders’ equity

Shares issued

During the six months ended June 30, 2024, the Company issued 1,064,286 shares of common stock upon vesting of Restricted Stock Units ("RSUs") granted by the Company to management and employees, including 428,566 of reissued treasury stock. We withheld 456,646 shares to satisfy approximately $360,000 of employees’ tax obligations during the six months ended June 30, 2024. We treat shares of common stock withheld for tax purposes on behalf of our employees in connection with the vesting of RSUs in a similar manner as common stock repurchases and reported as treasury stock. 

During the six months ended June 30, 2024, the Company issued 79,547 shares of common stock upon vesting of RSUs granted to Board members.

During the six months ended June 30, 2024, the Company issued 68,882 shares of common stock pursuant to the employee stock purchase plan.

During the six months ended June 30, 2024, the Company issued 5,039,383 shares of common stock pursuant to the at the market issuance sales agreement for net proceeds of $2.5 million.

In May 2024, the Company completed a public offering of 20,125,000 shares of its common stock at the public offering price of $0.39 per share. In connection with the sale of common stock, the Company issued warrants to purchase shares of common stock at the rate of one warrant for every share of purchased common stock, at the offering price of $0.01 per warrant. After the deduction of the underwriter’s discount and expenses payable by us, we received net proceeds of $7.3 million. The Company used the relative fair value method to allocate the net proceeds of approximately $7.3 million between the common stock and the warrants. As presented below, the Company recorded the fair value of the warrants of $3.1 million and common stock of $4.2 million.

Warrant issued

In connection with the above-described May 2024 public offering, the Company issued a warrant to purchase 782,500 shares of the Company's common stock to the underwriter of the Company's public offering, equal to 2% of the 20,125,000 shares sold, for relative fair value of $0.1 million. The warrants are exercisable at $0.4875 per share on the closing date,  May 14, 2024. The warrants have an expiration date of 5 years from the date of issuance and will expire on  May 14, 2029. The relative fair value of the warrants was recorded in the condensed consolidated balance sheet in additional paid-in capital in stockholders' equity as the warrants are indexed to the Company’s common stock and meet the conditions for equity classification.

In May 2024, in conjunction with the Company's public offering, the Company issued a warrant to purchase up to 20,125,000 shares of the Company's common stock, for the relative fair value of $3 million. The warrants are exercisable at $0.39 per share. The warrants have an expiration date of 5 years from the date of issuance and will expire on May 14, 2029. The relative fair value of the warrants was recorded in the condensed consolidated balance sheet in additional paid-in capital in stockholders' equity as the warrants are indexed to the Company’s common stock and meet the conditions for equity classification.

Stock-based compensation

The stock-based compensation expense was allocated as follows:

2014 Stock Incentive Plan

We have adopted the Aqua Metals, Inc. 2014 Stock Incentive Plan providing for the grant of non-qualified stock options and incentive stock options to purchase shares of our common stock and for the grant of restricted and unrestricted share grants. All of our officers, directors, employees and consultants are eligible to participate under the plan. The purpose of the plan is to provide eligible participants with an opportunity to acquire an ownership interest in our company. As of  June 30, 2024, there were 635,215 remaining shares available for future grants.

2019 Stock Incentive Plan

In 2019, our board of directors adopted the Aqua Metals, Inc. 2019 Stock Incentive Plan (the “2019 Plan”). A total of 18,500,000 shares of common stock was authorized for issuance pursuant to the 2019 Plan. The 2019 Plan provides for the following types of stock-based awards: incentive stock options; non-statutory stock options; restricted stock; and performance stock. The 2019 Plan, under which equity incentives may be granted to employees and directors under incentive and non-statutory agreements, requires that the option price may not be less than the fair value of the stock at the date the option is granted. Option awards are exercisable until their expiration, which may not exceed 10 years from the grant date. As of  June 30, 2024, there were 1,162,624 remaining shares available for future grants.

Restricted stock units

During the first quarter of 2024, the Company granted 111,522 RSUs, all of which were subject to vesting, with a grant date fair value of $60,000 to employees. The shares vest in three equal installments over a three-year period.

During the second quarter of 2024, the Company granted 125,000 RSUs, all of which were subject to vesting, with a grant date fair value of $40,000 to employees. The shares vest in three equal installments over a three-year period.